Method and apparatus for receiving multimedia broadcast/multicast service in mobile communication system

ABSTRACT

An MBMS service reception method and an apparatus are provided for facilitating reception of Multimedia Broadcast/Multicast Service (MBMS) provided in the Long Term Evolution (LTE) system. The method for receiving MBMS in a radio communication system includes receiving User Service Description (USD) information including time information of the MBMS in a connected mode, determining whether a session of the MBMS has started based on the time information, and receiving, when the MBMS session has started, MBMS data of the MBMS session. The MBMS service reception method and apparatus of the present invention facilitates receiving the MBMS service.

PRIORITY

This application is a continuation application of a prior applicationSer. No. 13/585,368, filed on Aug. 14, 2012, which claimed the benefitunder 35 U.S.C. § 119(e) of a U.S. Provisional application filed on May14, 2012 in the United States Intellectual Property Office and assignedSer. No. 61/646,473, and a U.S. Provisional application filed on Feb.22, 2012 in the United States Intellectual Property Office and assignedSer. No. 61/602,047, and a U.S. Provisional application filed on Aug.16, 2011 in the United States Intellectual Property Office and assignedSer. No. 61/524,000, the entire disclosure of each of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a mobile communication system. Moreparticularly, the present invention relates to a method and apparatusfor receiving Multimedia Broadcast/Multicast Service (MBMS) provided inthe Long Term Evolution (LTE) system.

2. Description of the Related Art

With the rapid advance of radio communication technologies,communication systems have evolved in stepwise manner. The Long TermEvolution (LTE) system is a representative 4th generation mobilecommunication system. The LTE system supports diverse services includingbroadcast services.

The LTE system supports the Multimedia Broadcast/Multicast Service(MBMS) such that the terminal supporting MBMS is capable of receivingthe MBMS service subscribed by the user within the network providing theMBMS service.

However, the MBMS service of the related art has a drawback in that itis difficult to determine whether a specific MBMS service session hasstarted with the MBMS service protocol. Also, when the MBMS service isprovided on multiple frequencies, there is a need of defining the rulefor the terminal to select the base station operating on one of thefrequencies.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present invention.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present invention toprovide a method and apparatus for determining whether the MultimediaBroadcast/Multicast Service (MBMS) service session has started in thewireless mobile communication system providing the MBMS service bytransmitting data on more than one uplink carrier.

Another aspect of the present invention to provide a method andapparatus for the terminal receiving the MBMS service to stay on thefrequency carrying the MBMS service while moving.

In accordance with an aspect of the present invention, a method forreceiving Multimedia Broadcast/Multicast Service (MBMS) in a radiocommunication system is provided. The method includes receiving UserService Description (USD) information including time information of theMBMS in a connected mode, determining whether a session of the MBMS hasstarted based on the time information, and receiving, when the MBMSsession has started, MBMS data of the MBMS session.

In accordance with another aspect of the present invention, a method forreceiving Multimedia Broadcast/Multicast Service (MBMS) in a radiocommunication system is provided. The method includes selecting a basestation to camp on after entering an idle mode, determining, when anMBMS session starts, whether User Service Description (USD) informationincluding frequency information of the MBMS is stored, performing, whenthe USD information is stored, cell reselection based on the frequencyinformation, and receiving MBMS data of the MBMS session from thereselected cell.

In accordance with another aspect of the present invention, a terminalfor receiving Multimedia Broadcast/Multicast Service (MBMS) in a radiocommunication system is provided. The terminal includes a transceiverfor transmitting and receiving data, and a controller for controllingreception of User Service Description (USD) information including timeinformation of the MBMS in a connected mode, for determining whether asession of the MBMS has started based on the time information, and forreceiving, when the MBMS session has started, MBMS data of the MBMSsession.

In accordance with another aspect of the present invention, a terminalfor receiving Multimedia Broadcast/Multicast Service (MBMS) in a radiocommunication system is provided. The terminal includes a transceiverwhich transmits and receives data, a storage which stores User ServiceDescription (USD) information, and a controller which controls selectinga base station to camp on after entering an idle mode, determining, whenan MBMS session starts, whether User Service Description (USD)information including frequency information of the MBMS is stored,performing, when the USD information is stored, cell reselection basedon the frequency information, and receiving MBMS data of the MBMSsession from the reselected cell.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram illustrating the architecture of an LTE systemaccording to an exemplary embodiment of the present invention;

FIG. 2 is a diagram illustrating a protocol stack of the LTE systemaccording to an exemplary embodiment of the present invention;

FIG. 3 is a diagram illustrating an exemplary situation of carrieraggregation in the LTE system according to an exemplary embodiment ofthe present invention;

FIG. 4 is a signaling diagram illustrating an MBMS service receptionmethod of a UE according to an exemplary embodiment of the presentinvention;

FIG. 5 is a flowchart illustrating a UE procedure for receiving MBMSservice according to an exemplary embodiment of the present invention;

FIG. 6 is a signaling diagram illustrating an MBMS service receptionmethod of a UE according to an exemplary embodiment of the presentinvention;

FIG. 7 is a signaling diagram illustrating an MBMS service receptionmethod of a UE according to an exemplary embodiment of the presentinvention;

FIG. 8 is a flowchart illustrating a frequency selection procedure ofthe UE for receiving MBMS service according to an exemplary embodimentof the present invention;

FIG. 9 is a block diagram illustrating a configuration of a UE accordingto an exemplary embodiment of the present invention; and

FIG. 10 is a block diagram illustrating a configuration of the eNBaccording to an exemplary embodiment of the present invention.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding, but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purposes only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

FIG. 1 is a diagram illustrating the architecture of an LTE systemaccording to an exemplary embodiment of the present invention.

Referring to FIG. 1, the radio access network of the mobilecommunication system includes evolved Node Bs (eNBs) 105, 110, 115, and120, a Mobility Management Entity (MME) 125, and a Serving-Gateway(S-GW) 130. The User Equipment (UE) 135 connects to an external networkvia eNBs 105, 110, 115, and 120 and the S-GW 130.

The eNBs 105, 110, 115, and 120 correspond to legacy node Bs ofUniversal Mobile Communications System (UMTS). The eNBs 105, 110, 115,and 120 allow the UE to establish a radio link and are responsible forcomplicated functions as compared to the legacy node B. In the LTEsystem, all the user traffic including real time services such as Voiceover Internet Protocol (VoIP) are provided through a shared channel andthus there is a need of a device which is located in the eNB to scheduledata based on the state information such as UE buffer conditions, powerheadroom state, and channel state.

Typically, one eNB controls a plurality of cells. In order to secure adata rate of up to 100 Mbps, the LTE system adopts Orthogonal FrequencyDivision Multiplexing (OFDM) as a radio access technology. The LTEsystem adopts Adaptive Modulation and Coding (AMC) to determine themodulation scheme and channel coding rate in adaptation to the channelcondition of the UE. The S-GW 130 is an entity to provide data bearersso as to establish and release data bearers under the control of the MME125. The MME 125 is responsible for various control functions andconnected to a plurality of eNBs 105, 110, 115, and 120.

FIG. 2 is a diagram illustrating a protocol stack of an LTE systemaccording to an exemplary embodiment of the present invention.

Referring to FIG. 2, the protocol stack of the LTE system includesPacket Data Convergence Protocol (PDCP) 205 and 240, Radio Link Control(RLC) 210 and 235, Medium Access Control (MAC) 215 and 230, and Physical(PHY) 220 and 225.

The PDCP 205 and 240 is responsible for IP headercompression/decompression, and the RLC 210 and 235 is responsible forsegmenting the PDCP Protocol Data Unit (PDU) into segments inappropriate size for Automatic Repeat Request (ARQ) operation. ARQ is aprocess for determining whether the packet transmitted by thetransmitted is received by the received successfully and retransmittingthe packets received erroneously. The MAC 215 and 230 is responsible forestablishing connection to a plurality of RLC entities so as tomultiplex the RLC PDUs into MAC PDUs and demultiplex the MAC PDUs intoRLC PDUs. The PHY 220 and 225 performs channel coding on the MAC PDU andmodulates the MAC PDU into OFDM symbols to transmit over radio channelor performs demodulating and channel-decoding on the received OFDMsymbols and delivers the decoded data to the higher layer.

The PHY layer uses Hybrid ARQ (HARQ) for additional error correction bytransmitting 1 bit information indicating for positive or negativeacknowledgement from the receiver to the transmitter. This is referredto as HARQ ACK/NACK information. The downlink HARQ ACK/NACK informationcorresponding to the uplink transmission is transmitted on the PhysicalHybrid-ARQ Indicator Channel, and the uplink HARQ ACK/NACK informationmay be transmitted on the Physical Uplink Control CHannel (PUCCH) orPhysical Uplink Shared Channel (PUSCH).

FIG. 3 is a diagram illustrating an exemplary situation of carrieraggregation in an LTE system according to an exemplary embodiment of thepresent invention is applied.

Referring to FIG. 3, an eNB typically uses multiple carriers transmittedand received in different frequency bands. For example, the eNB 305 maybe configured to use the carrier 315 with center frequency f1 and thecarrier 310 with center frequency f3. If carrier aggregation is notsupported, the UE 330 has to transmit/receive data unit one of thecarriers 310 and 315. However, the UE 330 having the carrier aggregationcapability may transmit/receive data using both the carriers 310 and315. The eNB may increase the amount of the resource to be allocated tothe UE having the carrier aggregation capability in adaptation to thechannel condition of the UE so as to improve the data rate of the UE.The technique of aggregating the downlink and uplink carriers isreferred to as carrier aggregation.

The terms used frequently in the description are explained below.

When a cell is configured with one downlink carrier and one uplinkcarrier, the carrier aggregation may be understood as if the UEcommunicates data via multiple cells. With the use of carrieraggregation, the maximum data rate increases in proportion to the numberof aggregated carriers.

In the following description, the phrase “the UE receives data through acertain downlink carrier” or “the UE transmits data through a certainuplink carrier” denotes transmitting or receiving data through controland data channels provided in a cell corresponding to center frequenciesand frequency bands of the downlink and uplink carriers. Although thedescription herein is directed to an LTE mobile communication system forconvenience of explanation, exemplary embodiments of the presentinvention may be applied to other types of wireless communicationsystems supporting carrier aggregation.

The User Service Description (USD) is a protocol defined fortransmitting to the UE receiving MBMS service the information on thebroadcast service (program information and schedules). The USD istransmitted to the UE using higher layer protocol such as HypertextTransfer Protocol (HTTP) and provides the UE with the information on theprograms and broadcast schedule.

FIG. 4 is a signaling diagram illustrating an MBMS service receptionmethod of a UE according to an exemplary embodiment of the presentinvention.

The UE 401 connects to the eNB 403 such that the UE 401 and the eNB 403enter the connected mode at step 411. In the connected mode, the UE 401is capable of communicating data with the eNB 403. Afterward, the eNB401 receives User Service Description (USD) information from the server405 at step 413.

The USD information is the protocol defined in Extensible MarkupLanguage (XML) for transmitting the information on the broadcast service(program information, program schedule, etc.) and transmitted to the UEthrough a higher layer protocol such as Hypertext Transfer Protocol(HTTP). The UE 401 is capable of acquiring the information on thebroadcast times of the programs and the frequency bands carrying therespective broadcast programs based from the USD information.

In the following description with reference to FIG. 4, it is assumedthat the user receives a broadcast of session A on which information isincluded in the USD information for the simplicity purpose. Theinformation on the session A is capable of including the timeinformation on the session A (e.g. the session A will be on air between3 and 4 PM).

After receiving the USD information, the UE 401 is capable of staying inthe connected mode or transitioning to the idle mode at step 415.

Among the eNBs providing the MBMS services, a set of the eNBs providingthe same service is referred to as Multimedia Broadcast/Multicastservice Single Frequency Network (MBSFN) and broadcasts the sameMBSFN-related resource allocation and session information.

The UE 401 determines, based on the time information about a specificsession (session A in this example) included in the received USDinformation, whether the session has started and, if so, receives theMBMS service at step 416. The UE 401 is capable of performing cellreselection to an eNB providing the service session to receive.

According to an exemplary embodiment of the present invention, the UE401 obtains the time information included in the USD information todetermine the start time of session A at 3 AM and starts receiving theMBMS service. If the MBMS session has not started, the UE determines,based on the time information about the MBMS session, whether the MBMSsession is ongoing and if so, selects the eNB providing the MBMS serviceas the cell reselection target eNB based on the MBMS session frequencyinformation to receive the MBMS service of the MBMS session.

The MBMS service reception procedure is as follows. The UE is capable ofreceiving a System Information Block (SIB) including the indicationindicating the Multimedia Broadcast multicast service Single FrequencyNetwork (MBSFN) subframe and another SIB including the resourceallocation location information carrying Multicast Control Channel(MCCH) and the indicator indicating the location of the subframe usedfor carrying the MBSFN data and the session information on the currentlyprovided service, MCCH based on the information included in the latterSIB, and the MBSFN data based on the MCCH.

The UE 401 receives the System Information Block 2 (SIB2) from the eNB403 at step 417. The MBSFN-SubframeConfigList IE included in the SIB2indicates the subframes that may be used for the purpose of MBSFNtransmission. The MBSFN-SubframeConfigList IE includesMBSFN-SubframeConfig IE which indicates which subframes of which radioframes may be used as the MBSFN subframes. The MBSFN-SubframeConfig IEincludes radioFrameAllocationPeriod and radioFrameAllocationOffsetparameters in order to indicate which radio frame is MBSFN-relatedframe, and the MBMS service is provided in the radio frame satisfyingEquation (1):SFN mod radioFrameAllocationPeriod=radioFrameAllocationOffset  (1)where SFN denotes a System frame number indicating the radio framenumber and repeats in the range from 0 to 1023.

The MBSFN-SubframeConfig IE also includes a subframeAllocation parameterindicating the MBSFN-related subframe in the form of a bitmap toindicate which subframe is MBSFN subframe in the radio frame indicatedby Equation (1).

The MBSFN subframe may be indicated in unit of one radio frame or fourradio frames. In the case of using one radio frame unit, oneFrame IE isused. The MBSFN subframe may be one of the 1st, 2nd, 3rd, 6th, 7th, and8th subframes among the total 10 subframes constituting one radiosubframe. Accordingly, oneFrame IE indicates the MBSFN subframes amongthe above enumerated subframes using 6 bits. In the case of using fourradio frames unit, fourFrames IE is used. In order to cover the fourradio frames, total 24 bits are used to indicate the MBSFN subframesamong the above enumerated subframes of each radio frame. Accordingly,the UE 401 is capable of identifying the subframes that may be used asMBSFN subframes based on the MB SFN-SubframeConfigList IE.

If it is intended to receive the MBMS service, the UE 401 receives SIB13from the eNB 403 at step 419. The MBSFN-AreaInfoList IE of the SIB13includes the resource allocation location information for transmittingthe multicast control channel (MCCH) per MBSFN area that is provided bythe cell. The UE 401 receives the MCCH using the resource allocationlocation information at step 421.

The MBSFNAreaConfiguration IE of the MCCH includes the indicatorindicating the location of the subframe used for MBSFN data transmissionin the MBSFN area and the information on the session of the currentservice. The UE 401 is capable of receiving specific MBSFN subframesusing such information. If the service of session A is not received eventhough the session is ongoing (i.e. current time is between the starttime and the end time), the UE 401 performs cell reselection based onthe frequency information in the USD information received at step 413rather than immediately.

After receiving the specific MBSFN subframe based on the informationincluded in the mbsfnAreaConfiguration IE of the MCCH, the UE 401receives the control message, i.e. MCH scheduling information MACControl Element, to identify the location of the actual MBSFN subframecarrying the interested data.

Through the above procedure, the UE 401 is capable of receiving theMBSFN data at steps 441, 443, and 445. The MBMS service reception methodaccording to an exemplary embodiment of the present invention isadvantageous to receive the service at an intended time based on the USDinformation received at step 413 without needing to determine whetherthe current session A is actually serviced by receiving the MCCHcarrying the MBSFNAreaConfiguration information for receiving theintended service of session A.

FIG. 5 is a flowchart illustrating a UE procedure for receiving MBMSservice according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the UE first receives the USD information in theconnected mode at step 501. As described above with reference to FIG. 4,the USD information includes the information related to the broadcastservice (program information, time schedule, etc.). The UE is capable ofidentifying the information on the start and end times of the serviceintended to receive and frequency carrying the corresponding servicebased on the USD information.

The UE determines whether the start time of the service intended toreceive arrives based on the USD information at step 503. If it isdetermined that the start time of the MBMS session has arrived, the UEstarts receiving the service of the session at the start time, althoughno MBSFN-related information is received additionally, at step 505. TheUE is capable of performing cell reselection procedure to the eNB usingthe frequency carrying the MBMS service based on the frequencyinformation included in the received USD information and receiving theMBMS service through a series of processes.

FIG. 6 is a signaling diagram illustrating an MBMS service receptionmethod of a UE according to another exemplary embodiment of the presentinvention.

Referring to FIG. 6, the description is made of the case of a UE 601capable of receiving the service on only one carrier and another UE 603capable of receiving the service on multiple carriers separately withreference to FIG. 6. The UE capable of receiving service on multiplecarriers may be a UE capable of carrier aggregation.

A description is made of the UE 601 capable of receiving service on asingle carrier. The UE 601 connects to the eNB 1 605 to enter theconnected mode at step 621. In the connected mode, the UE 601 is capableof communicating data with the eNB 605. The UE 601 in connected modereceives the USD information from the server 613 at step 623.

As described above, the USD information is a protocol defined in XML totransmit the information on the broadcast service (program information,broadcast schedule, etc.) and transmitted to the UE 601 using the higherlayer protocol such as HTTP. The UE 601 is capable of identifying thebroadcast programs and the service times of the broadcast programs andfrequencies carrying the services.

In the following description, it is assumed that the user is interestedin receiving session B broadcast and the USD information includes theinformation on the session B. The information on the session B mayinclude the information on the frequency of the session B (e.g. sessionB is serviced on frequency f2). The frequency information may beexpressed as E-UTRA Absolute Radio Frequency Channel Number (EARFCN) toprovide the UE with accurate frequency information.

The UE 601 enters the idle mode at step 625. The UE 601 in idle modeselects an eNB to camp on according to the cell reselection rule forroaming across cells. In FIG. 6, it is assumed that the UE 601 operateson the serving frequency f1 with neighbor frequencies f2, f3, and f4 andthe interested MBMS session is established on the frequency f2. The eNBs607, 609, and 611 operate on the neighbor frequencies f2, f3, and f4,respectively.

The UE 601 knows that the interested session is serviced on thefrequency f2 and thus configures the priority of f2 to the highestpriority at the start time of the session based on the USD informationat step 627. The UE 601 is also capable of identifying the broadcasttime 629 of the session B intended to receive based on the USDinformation. The UE receiving or intended to receive the MBMS service onthe MBSFN f2 is capable of receiving the MBMS service on only the aboveMBSFN, the corresponding frequency is configured to keep the highestpriority for the UE to continue receiving the MBMS service. The UE 601performs cell reselection onto f2 to receive the MBMS services from theeNB 2 at step 631 and 633.

A description is made of the UE 603 capable of receiving the service onmultiple carriers simultaneously. The UE 603 connects to the eNB 605 toenter the connected mode at step 641. In the connected mode, the UE 603is capable of communicating data with the eNB 605. The UE 603 inconnected mode receives the USD information from the server 613 at step643.

The UE 603 enters the idle mode at step 645. The UE 603 in idle modeselects an eNB to camp one according to the cell reselection rule forroaming across cells.

The UE 603 knows that the interested session is serviced on thefrequency f2 and thus determines whether it is possible to receive theservice additionally on the frequency f2 on the frequency band of f1 towhich the UE 603 has camped on at step 647. If it is determined that theUE is capable of receiving the service on both the frequencies f1 andf2, the UE 603 performs the cell reselection method of the related art.The UE 603 sets the priority of the f2 to the highest priority at thestart time of the session and performs cell reselection. The UE 603 iscapable of identifying the broadcast time 649 of the session B intendedto receive based on the USD information.

In FIG. 6, it is assumed that, when it has camped on f1, the UE 603 iscapable of receiving the service on f2 simultaneously. In this case,since the UE 603 has camped on f1, the UE 603 receives the pagingmessage from the eNB 1 605 to determine whether new downlink data occursperiodically at step 651. Since the UE 603 is capable of receiving theservice on multiple carriers, the UE 603 may receive the UE-interestedMBMS service from neighbor cells at steps 653 and 655, using thefrequency information (here, frequency f2) in the USD informationreceived at step 643.

It is assumed that the UE 603 capable of receiving on multiplefrequencies moves so as to perform cell reselection again. If it isnecessary to perform cell reselection, the UE 603 determines whether itis possible to receive the service on another frequency along with f2simultaneously as in the above case. In FIG. 6, it is assumed that thesimultaneous reception from eNBs other than f2 is impossible. The UE 603sets the priority of f2 to the highest and performs cell reselection.That is, the UE 603 camps on the eNB 2 607 at step 657. Accordingly, theUE 603 receives the paging message from the eNB 2 607 periodically atstep 659 to determine whether new downlink data occurs and continuesreceiving MBMS data from the eNB 2 607 at steps 661 and 663.

FIG. 7 is a signaling diagram illustrating an MBMS service receptionmethod of a UE according to another exemplary embodiment of the presentinvention.

Referring to FIG. 7, the description is made of the case of a UE 701capable of receiving the service on only one carrier and another UE 703capable of receiving the service on multiple carriers separately withreference to FIG. 7. The UE capable of receiving service on multiplecarriers may be a UE capable of carrier aggregation.

A description is made of the UE 701 capable of receiving service on asingle carrier. The UE 701 connects to the eNB 705 at step 721 to enterthe connected mode at step 721. In the connected mode, the UE 701 iscapable of communicating data with the eNB 705. The UE 701 in connectedmode receives the USD information from the server 713 at step 723.

As described above, the USD information is a protocol defined in XML totransmit the information on the broadcast service (program information,broadcast schedule, etc.) and transmitted to the UE 701 using the higherlayer protocol such as HTTP. The UE 701 is capable of identifying thebroadcast programs and the service times of the broadcast programs andfrequencies carrying the services.

In the following description, it is assumed that the user is interestedin receiving session B broadcast and the USD information includes theinformation on the session B. The information on the session B mayinclude the information on the frequency of the session B (e.g. sessionB is serviced on frequencies f2 and f3). The frequency information maybe expressed as E-UTRA Absolute Radio Frequency Channel Number (EARFCN)to provide the UE with accurate frequency information.

The UE 701 enters the idle mode at step 725. The UE 701 in idle modeselects an eNB to camp on according to the cell reselection rule forroaming across cells. In FIG. 7, it is assumed that the UE 701 operateson the serving frequency f1 with neighbor frequencies f2, f3, and f4 andthe interested MBMS session is established on the frequencies f2 and f3.The eNBs 707, 709, and 711 operate on the neighbor frequencies f2, f3,and f4, respectively.

The UE 701 knows that the interested session is serviced on thefrequencies f2 and f3 and thus configures the priority of at least oneof f2 and f3 to the highest priority at the start time of the sessionbased on the USD information at step 727. The UE 701 is also capable ofidentifying the broadcast time 729 of the session B intended to receivebased on the USD information. The UE 701 receiving or intended toreceive the MBMS service on the MBSFN f2 or f3 is capable of receivingthe MBMS service in only the above MBSFN, the corresponding frequency isconfigured to keep the highest priority for the UE to continue receivingthe MBMS service. The UE 701 performs cell reselection onto f2 toreceive the MBMS services from the eNB 2 at step 731 and 733.

A description is made of the UE 703 capable of receiving the service onmultiple carriers simultaneously. The UE 703 connects to the eNB 705 toenter the connected mode at step 741. In the connected mode, the UE 703is capable of communicating data with the eNB 705. The UE 703 inconnected mode receives the USD information from the server 713 at step743.

The UE 703 enters the idle mode at step 745. The UE 603 in idle modeselects an eNB to camp on according to the cell reselection rule forroaming across cells.

The UE 703 knows that the interested session is serviced on thefrequency f2 and thus determines whether it is possible to receive theservice additionally on the frequency f2 or f3 on the frequency band off1 to which it has camped on at step 747.

If it is determined that the UE is capable of receiving the service onthe frequencies f1 and one of f2 and f3, the UE 703, performs the cellreselection method of the related art. The UE 703 sets the priority ofthe f2 or f3 to the highest priority at the start time of the sessionand performs cell reselection. The UE 703 is capable of identifying thebroadcast time 749 of the session B intended to receive based on the USDinformation.

In FIG. 7, it is assumed that, when it has camped on f1, the UE 603 iscapable of receiving the service on f1 and one of f2 and f3simultaneously. In this case, since it has camped on f1, the UE 703receives the paging message from the eNB 1 705 to determine whether newdownlink data occurs periodically at step 751. Also, since the UE 703 iscapable of receiving the service on multiple carriers, the UE 703 mayreceive the UE-interested MBMS service from neighbor cells at steps 753and 755, using the frequency information (here, frequencies f2 and f3)in the USD information received at step 743. In FIG. 7, it is depictedthat the service is received from the eNB 2 707.

Suppose that the UE 703 capable of receiving on multiple frequenciesmoves so as to perform cell reselection again. If it is necessary toperform cell reselection, the UE 703 determines whether it is possibleto receive the service on other frequency along with f2 or f3simultaneously as in the above case. In FIG. 7, it is assumed that thesimultaneous reception from other eNB than f2 or f3 is impossible. TheUE 703 sets the priorities of f2 and f3 to the highest and performs cellreselection. That is, the UE 703 camps on the eNB 2 707 or eNB 3 709 atstep 757. Accordingly, at step 759, the UE 703 receives the pagingmessage from the eNB 2 707 or the eNB 3 709 periodically to determinewhether new downlink data occurs and continues receiving MBMS data fromthe eNB 2 707 or the eNB 3 709 at steps 761 and 763. In FIG. 7, it isdepicted that the service is received from the eNB 707.

FIG. 8 is a flowchart illustrating a frequency selection procedure ofthe UE for receiving MBMS service according to an exemplary embodimentof the present invention.

The UE first enters the idle mode at step 801. The UE determines whetherthe USD information has been previously received from the server at step803. The USD information is capable of including the information on thefrequency carrying the MBMS service. If it is determined that there isno previously stored USD information at step 803, the UE performs thecell reselection according to the related art (i.e., select new eNB whencell reselection is required due to a reason such as roaming approval)at step 807.

Otherwise, if it is determined that there is previously stored USDinformation at step 803, the UE determines whether it supports multiplecarrier reception at step 805. If it is determined that the UE supportsmultiple carrier reception at step 805, the procedure goes to step 811and, otherwise, step 813. The multiple carrier reception capability maybe determined by the UE or an embedded feature of the UE. In case thatthe multiple carrier reception capability is the feature of the UE, step805 may be omitted and the procedure goes to step 811 for the UE capableof single carrier reception and step 813 for the UE capable of multiplecarrier reception.

At step 811 for cell reselection, the UE selects one of the eNBscorresponding to the cells operating on the frequencies indicated by thestored USD information to receive the MBMS service on the correspondingfrequency.

At step 813 for cell reselection, the UE determines whether it ispossible to receive the service on another frequency along with thecurrent frequency on which the MBMS service is provided based on the USDinformation. If it is possible to receive the service on anotherfrequency along with the current frequency, the UE performs cellreselection according to the conventional cell reselection method(select new eNB when cell reselection is required due to a reason suchas roaming approval) at step 809; however, since it is possible toreceive the service on multiple carriers, the UE adds the frequency bandindicated by the stored USD information and receive the MBMS service onthe corresponding frequency.

If it is determined that the UE cannot receive the service on anotherfrequency (i.e. it is impossible to select a frequency other than thefrequency carrying the MBMS service), the procedure goes to step 811 atwhich the UE selects the eNB corresponding to one of the cells operatingon the frequencies indicated by the stored USD information and receivesthe MBMS service on the corresponding frequency.

FIG. 9 is a block diagram illustrating a configuration of a UE accordingto an exemplary embodiment of the present invention.

Referring to FIG. 9, the UE includes a transceiver 905, a controller910, a storage unit 915, a multiplexer/demultiplexer 920, higher layerprocessors 925 and 930, and a control message processor 935. The UE mayinclude additional units not shown here for the purpose of clarity.

The transceiver 905 receives data and control signals through a downlinkchannel of the serving cell and transmits data and control signalthrough an uplink channel. In the case that multiple serving cells areconfigured, the transceiver 905 is capable of transmitting and receivingdata con control signals through multiple serving cells.

The storage unit 915 is responsible for storing program data related tothe operations of the UE and may be divided into a program region and adata region. The storage unit 915 may be implemented with at least oneof volatile and nonvolatile storage media. The volatile media includesemiconductor memories such as RAM, DRAM, and SRAM, and the nonvolatilemedia include hard disk. In the present invention, the storage unit 915is capable of the received USD information.

The multiplexer/demultiplexer 920 multiplexes the data generated by thehigher layer processors 925 and 930, and the control message processor935, and demultiplexes the data received by the transceiver 905 todeliver the demultiplexed data to appropriate processors, i.e. thehigher layer processors 925 and 930, and the control message processor935.

The higher layer processors 925 and 930 are configured per service toprocess the data generated by a user service, such as File TransferProtocol (FTP) and Voice over Internet Protocol (VoIP). The higher layerprocessors 925 and 930 transfer the processed data to themultiplexer/demultiplexer 920, and process the data from themultiplexer/demultiplexer 920, and deliver the processed data to theservice application running on the higher layer.

The controller 910 identifying the scheduling command, e.g. uplinkgrant, received by the transceiver 905 and controls the transceiver 905and the multiplexer/demultiplexer 920 to perform uplink transmissionwith appropriate transmission resource at appropriate timing. Thecontroller 910 controls the transceiver by taking notice of the DRXoperation and CSI/SRS transmission. The controller 910 is capable ofcontrolling the overall operations for receiving the multimediabroadcast service in the radio communication system as described above.

FIG. 10 is a block diagram illustrating a configuration of the eNBaccording to an exemplary embodiment of the present invention.

Referring to FIG. 10, the eNB includes a transceiver 1005, a controller1010, a scheduler 1015, a multiplexer/demultiplexer 1020, various higherlayer processors 1025 and 1030 and a control message processor 1035. TheeNB may include additional units not shown here for purposes of clarity.

The transceiver 1005 transmits data and control signals on a downlinkcarrier and receives data and control signals on an uplink carrier. Whenmultiple carriers are configured, the transceiver 1005 transmits andreceives the data and control signals on the multiple carriers.

The multiplexer/demultiplexer 1020 multiplexes the data generated by thehigher layer processors 1025 and 1030 and the control message processor1035 and demultiplexes the data received by the transceiver 1005 todeliver the demultiplexed data to at least one of the higher layerprocessors 1025 and 1030 and the control message processor 1035 and thecontroller 1010. The control message processor 1035 processes themessage transmitted by the UE and takes a necessary action or generatesa control message to be transmitted to the UE to the higher layer.

The higher layer processors 1025 and 1030 are configured per UE perservice to process the data generated by a user service, such as FileTransfer Protocol (FTP) and Voice over Internet Protocol (VoIP). Thehigher layer processors 1025 and 1030 transfer the processed data to themultiplexer/demultiplexer 1020, process the data from themultiplexer/demultiplexer 1020, and deliver the processed data to theservice application running on the higher layer.

The controller 1010 controls the transceiver according to the CSI/SRStransmission timing of the UE.

The scheduler 1015 allocates transmission resource to the UE at anappropriate time in consideration of the buffer status of the UE,channel status, and active time of the UE; and controls the transceiverto process the signals transmitted by the UE or to be transmitted to theUE.

As described above, the MBMS service reception method and apparatusaccording to exemplary embodiments of the present invention is capableof facilitating reception of the MBMS service.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined in the appended claims and their equivalents.

What is claimed is:
 1. A method for performing a cell reselection by aterminal in a wireless communication system, the method comprising:receiving a user service description (USD) on a first frequency when theterminal is in a connected state; obtaining frequency informationindicating which frequency provides a Multimedia Broadcast/MulticastService (MBMS) service via a MBMS Single Frequency Network (MBSFN) whichthe terminal is interested in receiving, from the USD; determining, bythe terminal, a second frequency to be a highest priority frequencyduring an MBMS session corresponding to the MBMS service based on thefrequency information included in the USD if the frequency informationindicates that the terminal can only receive the MBMS service via theMBSFN while camping on the second frequency; and performing a cellreselection based on the highest priority frequency, when the terminalis in an idle state, to receive the MBMS service from a reselected cell.2. The method of claim 1, wherein the USD is provided through an upperlayer.
 3. The method of claim 1, wherein the USD includes timeinformation of a start and an end of an MBMS session.
 4. The method ofclaim 1, further comprising: identifying that the MBMS service cannot bereceived on the first frequency based on the frequency information.
 5. Aterminal for performing a cell reselection in a wireless communicationsystem, the terminal comprising: a transceiver configured to transmitand receive data; and a controller configured to: receive, via thetransceiver, a user service description (USD) on a first frequency whenthe terminal is in a connected state, obtain frequency informationindicating which frequency provides a Multimedia Broadcast/MulticastService (MBMS) service via a MBMS Single Frequency Network (MBSFN) whichthe terminal is interested in receiving, from the USD, determine asecond frequency to be a highest priority frequency during an MBMSsession corresponding to the MBMS service based on the frequencyinformation included in the USD if the frequency information indicatesthat the terminal can only receive be received the MBMS service via theMBSFN while camping on the second frequency, and perform a cellreselection based on the highest priority frequency, when the terminalis in an idle state, to receive the MBMS service from a reselected cell.6. The terminal of claim 5, wherein the USD is provided through an upperlayer.
 7. The terminal of claim 5, wherein the USD includes timeinformation of a start and an end of an MBMS session.
 8. The terminal ofclaim 5, wherein the controller is configured to identify that the MBMSservice cannot be received on the first frequency based on the frequencyinformation.